Exosome-Carried microRNA-375 Inhibits Cell Progression and Dissemination via Bcl-2 Blocking in Colon Cancer

Background: Worldwide, colorectal cancer (CRC) is the third most common cancer in men and second in women. The aim of the current study was to identify whether the miR-375 is indeed down-regulated in metastatic CRC and if it could be considered as a potential minimally invasive prognostic biomarker for CRC. Methods. Exosomes were isolated and characterized from patients with liver metastasis from CCR. The characterization of exosome was performed using TEM/SEM. HCT116 cells were treated with miR-375 mimic, NSM and miR-375 inhibitor. Functional assays included cell counting assay for 14 days, Matrigel invasion assay, apoptosis assay by flow cytometry using Annexin V-FITC, RT-PCR and Western blotting. Results. Increased proliferation potential was proven for the cells transfected with miR-375 inhibitor, while the miR-375 mimic decreased the cell number. The cells transfected with the miR-375 inhibitor are aggressive and cross the membrane; 3.84% of the cells transfected with the miR-375 inhibitor entered apoptosis, while 6.45% of those transfected with the non-specific mimic were in programmed cell death, less than those transfected with the microRNA. RT-PCR for Bcl-2 expression showed that Bcl-2 is down-regulated for miR-375 inhibitor and up-regulated for the miR-375 mimic, a result confirmed by Western blotting. Conclusion: The present study brings to the forefront new data that suggest miR-375 as a new player in controlling the pathways responsible for inhibiting the natural history of CRC tumor cells, via the Bcl-2 pathway. Abbreviations: APC: adenomatous polyposis coli; CRC: colorectal cancer; EGFR: epidermal growth factor receptor; ERB: Erythroblastic Leukemia Viral Oncogene Homolog; FITC: Fluorescein isothiocyanate; MAPK: mitogen-activated protein-kinase; miR: microRNA; mTOR: mammalian target of rapamycin; NSM: non specific mimic; qRT-PCR: quantitative real time polymerase chain reaction; SEM: scanning electron microscopy; TEM: transmission electron microscopy; TGF-beta: transforming growth factor beta.